Spraying WC-Based Coating on AZ91 Using HVOF to Improve Wear and Corrosion Resistance

Two WC-10Co-4Cr and WC-12Co coatings were deposited on the surface of AZ91 magnesium alloy using high velocity oxygen fuel (HVOF) technology aiming to improve the wear resistance and corrosion resistance. The hardness and organization of the surface and cross section of the coating and substrate were compared. The differences in wear resistance and corrosion resistance between the coatings and the substrate were compared. The wear experiments showed that the wear volumes of WC-10Co4Cr, WC-12Co and AZ91 substrate were 2.7 x 10-3 mm3, 1.1 x 10-3 mm3 and 6.1 x 10-1 mm3, respectively. The coatings mainly exhibited abrasive wear and adhesive wear. The better wear resistance of the coatings than the AZ91 substrate is due to the high hardness of the coatings. The corrosion resistance of the coatings was better than that of the substrate, and the corrosion resistance of WC-10Co-4Cr was better than that of WC-12Co. The corrosion currents density of WC-10Co4Cr, WC-12Co and AZ91 substrates are 4.02 mu A cm-2, 34.31 mu A cm-2 and 46.79 mu A cm-2, respectively. The Cr element is favorable for further improving the corrosion resistance.